Anomalous L subshell ratios in mixed M1-E2 transitions

Abstract

The L subshell ratios of a number of M1-E2 transitions have been measured accurately with the Berkeley 50-cm iron free π √2 spectrometer. When the three L subshell conversion lines are resolved, the M1-E2 mixing ratio is overdetermined, because a unique value of δ 2 (i.e. E2/M1) is given by any one of the ratios L I/L II, L I/L III and L II/L III. (Algebraically only two of these ratios are independent.) Thus, if all three ratios are measured experimentally, the same value of δ 2 should in principle be obtained. In fact, this does not always appear to be the case. One of the most pronounced discrepancies is found in the case of the 103 keV transition in Eu 153. The measured ratios are L I/L II = 8.22±0.10, L I/L III = 20.65±0.28 and L II/L III = 2.51±0.05. With use of carefully interpolated values from Sliv's tables, the E2 admixtures obtained are 2.02±0.08, 1.66±0.3 and 1.44±0.06 percent, respectively. With Rose's values the E2 admixtures are 2.18±0.08, 1.52±0.03 and 1.15±0.06 percent. Similar discrepancies were observed in the 114 keV transition in Lu 175 and 42 and 52 keV transitions in Bk 249. Relatively good agreement with Sliv's values is found for the 69 keV transition in Eu 153 and for the 58 keV transition in Tb 159. The agreement is generally better with Sliv's than with Rose's values. The two sets of theoretical L conversion coefficients differ sometimes by as much as 50%.